require 'rupert/errors'
require 'rupert/parser'
require 'rupert/rpm/lead'
require 'rupert/rpm/signature'

require 'base64'

module Rupert
  class RPM
    class << self
      # Loads a RPM file and parses its structure
      #
      # @param filename [String] filename of the RPM to load
      # @return [Rupert::RPM] the parsed RPM
      def load(filename)
        raise NotAnRPM, 
          "File #{filename} isn't a valid RPM" unless rpm?(filename)

        raw_io = File.open(filename, 'r')
        rpm = Parser.new(raw_io).parse
        raw_io.close

        return rpm
      end

      # Tells whether given filename points to a valid RPM or not.
      #
      # @param filename [String] filename to inspect
      # @return `true` if file starts with the correct magic header
      def rpm?(filename)
        Lead.new(File.open(filename, 'r')).rpm?
      end
    end

    # Initialize the RPM object, given its components.
    #
    # This method is not intended to be used to instantiate RPM objects
    # directly. Instead, use Rupert::RPM::load for a more straightforward
    # alternative.
    #
    # @param lead [Rupert::RPM::Lead] RPM lead section
    # @param signature [Rupert::RPM::Signature] RPM signature section
    # @param content [String] Raw content found after the signature structure
    def initialize(lead, signature, content)
      @lead = lead
      @signature = signature
      @content = content
    end

    # RPM version used to encode the package.
    #
    # @return [String] the RPM version in `<major>.<minor>` format
    def rpm_version
      @lead.rpm_version
    end

    # @return `true` if the RPM is of type binary, `false` otherwise
    def binary?
      @lead.binary_type?
    end

    # @return `true` if the RPM is of type source, `false` otherwise
    def source?
      @lead.source_type?
    end

    # Which architecture the package was built for, e.g. `i386/x86_64` or
    # `arm`
    #
    # @return [String] package architecture name
    def rpm_arch
     @lead.arch
    end

    # Full package name
    #
    # @return [String] package name in the form <name>-<version>-<rev>.<suffix>
    def name
      @lead.name
    end

    # OS for which the package was built
    #
    # @return [String] as defined in /usr/lib/rpm/rpmrc under the canonical OS
    #         names section
    def os
      @lead.os
    end

    # @return `true` if the package is signed, `false` otherwise
    def signed?
      @lead.signed?
    end

    # MD5 checksum stored in the package (base64 encoded). To be used to check
    # package integrity.
    #
    # NOTE: This is not the MD5 of the whole package; rather, the digest is
    # calculated over the header and payload, leaving out the lead and the
    # signature header. I.e., running `md5sum <myrpm>` won't held the same
    # result as `Rupert::RPM.load('<myrpm>').md5`.
    #
    # @return [String] Base64-encoded MD5 checksum of package's header and
    #         payload, stored in the RPM itself
    def md5
      Base64.strict_encode64(@signature.md5)
    end

    # Verifies package integrity. Compares MD5 checksum stored in the package
    # with checksum calculated over header(s) and payload (archive).
    #
    # @return `true` if package is intact, `false` if package (either stored MD5 or
    # payload) is corrupted
    def intact?
      @signature.verify_checksum(@content)      
    end
  end
end